Human Tim8a and Tim8b are members of an intermembrane space chaperone network, known as the small TIM family. Mutations in TIMM8A cause a neurodegenerative disease, Mohr-Tranebjærg syndrome (MTS), which is characterised by sensorineural hearing loss, dystonia and blindness. Nothing is known about the function of hTim8a in neuronal cells or how mutation of this protein leads to a neurodegenerative disease. We show that hTim8a is required for the assembly of Complex IV in neurons, which is mediated through a transient interaction with Complex IV assembly factors, in particular the copper chaperone COX17. Complex IV assembly defects resulting from loss of hTim8a leads to oxidative stress and changes to key apoptotic regulators, including cytochrome c, which primes cells for death. Alleviation of oxidative stress with Vitamin E treatment rescues cells from apoptotic vulnerability. We hypothesise that enhanced sensitivity of neuronal cells to apoptosis is the underlying mechanism of MTS.

Mitochondria are iconic structures in biochemistry and cell biology, traditionally referred to as the powerhouse of the cell due to a central role in energy production. However, modern-day mitochondria are recognized as key players in eukaryotic cell biology and are known to regulate crucial cellular processes, including calcium signalling, cell metabolism and cell death, to name a few. In this review, we will discuss foundational knowledge in mitochondrial biology and provide snapshots of recent advances that showcase how mitochondrial function regulates other cellular responses.

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The ability of juvenile silver perch (Bidyanus bidyanus) to utilize dietary raw wheat meal, raw wheat starch, gelatinized wheat starch and dextrin as energy sources to spare protein for growth was quantified. Energy utilization and protein sparing were assessed by comparing the weight gain, energy retention efficiency, protein retention and body composition of silver perch that had been fed a series of diets in which the basal diet (low carbohydrate) was systematically replaced with graded levels of each carbohydrate ingredient or an inert diluent, diatomaceous earth. The protein content decreased as the carbohydrate content increased, giving four different protein to energy ratios for each of the four carbohydrate sources (except for the 60% inclusion level, at which only three carbohydrate sources were tested). Silver perch were efficient at utilizing carbohydrate for energy to spare protein. Silver perch fed diets containing up to 30% wheat meal, raw wheat starch, gelatinized wheat starch or dextrin exhibited similar growth, protein retention and energy retention efficiency to the fish fed the basal diet. Weight gain of silver perch fed diets containing wheat meal or carbohydrates at 45% inclusion content had significantly reduced weight gain when compared with fish fed the basal diet. However, protein retention and energy retention efficiency were similar or better. Whole-body protein levels of silver perch remained constant regardless of carbohydrate sources, and there was no evidence of increasing whole-body lipid concentrations for fish fed diets with up to 60% dietary carbohydrate. Silver perch were more efficient at utilizing processed starch (either gelatinized starch or dextrin) than wheat meal or raw wheat starch.

The ability of silver perch (Bidyanus bidyanus) to digest and utilize dietary starch or starch breakdown products was investigated. For experiment 1 the ability of silver perch (2.7 + 0.01 g) to digest wheat starch at two dietary inclusion levels (30% or 60%), each at four levels of gelatinization (0%, 25%, 50% or 80%), was investigated over a 31-day period. For experiment 2, the ability of silver perch (15.9+ 0.25 g) to digest wheat starch, dextrin (at three levels of dextrinization), maltose, glucose and pea starch, all at the 30% inclusion level, was investigated over a 41-day period. Water temperature for both experiments was 25 + 1 8C. Apparent digestibility coefficients (ADCs) for starch, dry matter (DM) and energy were affected by both degree of gelatinization (80% > 50% > 25% 0%) and inclusion level (30% > 60%). Specific growth rate (SGR) was unaffected by the inclusion of 30% starch; however, it was reduced at the 60% starch content level. Degree of gelatinization had no effect on SGR. For experiment 2, there were significant differences between carbohydrate and DM ADCs for the test ingredients. The carbohydrate, DM and energy ADCs were ranked as follows: dextrin (Fieldose 9) dextrin (Fieldose 17) dextrin (Fieldose 30) gelatinized wheat starch maltose glucose > raw wheat starch > raw pea starch. The protein ADC of the diets, postprandial plasma glucose concentration and SGR were all unaffected by ingredient type. For both experiments, HSI tended to increase with carbohydrate inclusion. Liver glycogen concentrations were also elevated, but muscle glycogen and liver and muscle triacylglycerol concentrations were unaffected. Digestibility of starch by silver perch is clearly affected by inclusion content and processing.

The effects of exogenous digestive enzyme supplements on the digestibility of wheat starch or diets containing either wheat or dehulled lupin (Lupinus angustifolius var. gungurra) by silver perch (Bidyanus bidyanus) were investigated. In the first experiment, Natustarch® (α‐amylase supplement specific to starch) was added at three nominal concentrations (0, 50, 100 or 150 mg kg−1 diet) to diets containing either raw or 100% gelatinized wheat starch (30% dietary inclusion content) and fed to silver perch. The apparent digestibility coefficients (ADCs) for dry matter, starch and energy were calculated. The action of Natustarch® on the diet and in the digestive tract was also investigated. The addition of Natustarch® to diets containing raw and gelatinized wheat starch led to an average increase in reducing sugar content of diets of 67% and 340% respectively, indicating that the α‐amylase was more efficient at hydrolysing wheat starch in the gelatinized form. Gelatinized wheat starch was digested more efficiently than raw wheat starch. However, although the addition of Natustarch® at ≥ 50 mg kg−1 led to a significant increase in digestibility of raw wheat starch; the digestibility of gelatinized wheat starch, which was already high, was not further improved. Leaching due to immersion in water caused a minor loss of α‐amylase activity from diet pellets treated with Natustarch® (∼ 13% after 5 min). The α‐amylase activity in the anterior section of the intestinal tract of silver perch fed diets containing Natustarch® was not affected, indicating that the α‐amylase had been denatured by the acidic conditions in the stomach of silver perch. In the second experiment, diets containing wheat or lupin (at the 30% inclusion content) were treated with Natugrain‐blend®[an enzyme supplement containing β‐glucanase and β‐xylanase, specific to non‐starch polysaccharides (NSPs)] at three nominal concentrations (0, 75, 150 or 300 μL kg−1) and fed to silver perch. ADCs for energy and protein were calculated. The addition of Natugrain‐blend® had no effect on dry matter, energy or protein digestibility of the diets or ingredients.

The majority of proteins localised to mitochondria are encoded by the nuclear genome, with approximately 1500 proteins imported into mammalian mitochondria. Dysfunction in this fundamental cellular process is linked to a variety of pathologies including neuropathies, cardiovascular disorders, myopathies, neurodegenerative diseases and cancer, demonstrating the importance of mitochondrial protein import machinery for cellular function. Correct import of proteins into mitochondria requires the co‐ordinated activity of multimeric protein translocation and sorting machineries located in both the outer and inner mitochondrial membranes, directing the imported proteins to the destined mitochondrial compartment. This dynamic process maintains cellular homeostasis, and its dysregulation significantly affects cellular signalling pathways and metabolism. This review summarises current knowledge of the mammalian mitochondrial import machinery and the pathological consequences of mutation of its components. In addition, we will discuss the role of mitochondrial import in cancer, and our current understanding of the role of mitochondrial import in neurodegenerative diseases including Alzheimer's disease, Huntington's disease and Parkinson's disease.

As part of preliminary work aimed at the development of a formulated diet for the mud crab, Scylla serrata, an experiment was conducted with juvenile mud crabs (95.65 AE 2.17 g) to determine apparent digestibility coe⁄cients (ADC) for cellulose, ¢sh meal, shrimp meal, blood meal, soybean meal, wheat £our and cod liver oil. Apparent digestibility coe⁄cients for dry matter (ADC dm ), energy (ADC energy ) and protein (ADC protein ) were in the ranges 70.0^95.7%, 77.4^97.1% and 57.7^97.9% respectively. Soybean meal had the highest ADC dm and wheat £our had the lowest value (Po0.05), while the ADC dm for ¢sh meal, blood meal and shrimp meal were not di¡erent (P ! 0.05). Similarly, soybean meal had the same AD-C energy as that of ¢sh meal, but higher than those of cod liver oil, blood meal and shrimp meal (Po0.05). Moreover, the ADC protein for blood meal or shrimp meal were not signi¢cantly di¡erent from ¢sh meal (P ! 0.05); nevertheless, they were lower than that of soybean meal and higher than that of wheat £our (Po0.05). Of signi¢cant interest was the ADC dm (78.0%) and ADC energy (77.4%) for cellulose, which indicates that plant-based nutrient sources may well be a useful component of formulated diets for mud crabs.